Electron tube generator



Aug. 27, 1957 A. o. PALMER ELECTRON TUBE GENERATOR 2 Sheets-Sheet 1 Filed Jan. 19, 1954 Y m M T. R V mm m A 8 L 1% VI, 7 2 2 m F Aug. 27, 1957 A. o. PALMER 2,804,563

ELECTRON TUBE GENERATOR Filed Jan. 19, 1954 2 Sheets-Sheet 2 FIG. 2

INVENTOR ALBERT O. PALMER BY 9mm ATTQRNEY United States Patent i 2,804,563 ELECTRON TUBE GENERATOR Albert 0. Palmer, Springdale, Conn, assignor to Machlett Laboratories, Incorporated, Springdale, Comm, a corporation of Connecticut Application January 19, 1954, Serial No. 404,967

2 Claims. (Cl. 313-180) This invention concerns a compact, effective gas generator for use in low pressure, gas filled electron tube applications.

In the prior art, gas generators have commonly consisted of a quantity of gas-generating material either sprayed onto a heater ribbon or filling a container, such as a nickel tube, which container is surrounded by a heater element. In either event loss of the powder from the generator into the tube has been a common cause of upset of tube characteristics. In the case of the ribbon type generator, it is also difficult to control the amount of gas generated because the rate of generation increases rapidly with current (i. e. heater temperature). On the other hand, the amount of gas-generating material which can be heated using a heater surrounding a nickel tube is limited to a shallow depth below the interior surface of the tube and the amount of surface exposed to said interior surface is relatively small. Then too, the escape from the tube of the gas generated is rendered difficult because ofthe relatively compact nature of the gas-generating powder and because, in order to obtain enough volume of generating material, it is necessary to make the cylinder of gas-generating material within the nickel tube quite long.

The present invention improves over the prior art structures in that it permits the effective use of the whole of a given volume of gas-generating material. Moreover, the gas generator unit as a whole in accordance with the present invention may be made quite small. Furthermore, the gas generating material held within a container in such a manner that the gas produced can easily escape therefrom while the gas generating material is itself held in its proper position.

In accordance with the present invention a hoilow dielectric cylinder or cup, preferably of ceramic of one type or another, is located coaxially within a tubular metal shell. This ceramic cylinder or cup is the only insulator provided for a filament which is contained within the hollow of the ceramic cylinder or cup and used to heat the cylinder or cup to the temperature of 1100 or 1200 C. The gas-generating material is preferably a sintered and highly porous form and located between the outside of the ceramic cylinder or cup and the metallic shell, thereby forming an annular or tubular configuration of gas-generating material. The exposed ends of this annular body of generating material are covered with annular mats or pads of highly porous material, such as steel wool, or other metallic wool, which mats extend between the cylinder and the shell members. Holding these porous members in place are sheet metal annuli having perforations therethrough which permit the escape of gas generated by gas-generating material. These annuli extend between the shell and the ceramic cylinder, thereby providing end walls or baflles to hold the gasgenerating material in place.

For a better understanding of the present invention reference is made to the following drawings:

Fig. 1 illustrates in partial section a gas filled electron .i atented Aug. 27, 1957 tube of the hydrogen thyratron variety, showing in section apreferred type of gas-generating element of this invention.

Fig. 2 shows in axial section the same novel gasgenerating element shown in Fig. 1.

Fig. 3 is a plan View of the gas generator element showing the closure means provided for the open end of the hollow ceramic cylinder and other details.

Fig. 4 is a perspective view of the closure means for the ceramic cylinder and the connection means which extend therefrom.

Referring now to Fig. 1 it may be seen that various tube' elements are located within vacuum envelope 10 which is filled with a low pressure gas. Supported from one end of the envelope and forming a reentrant portion thereof is tubular support member 11 which supports and is closed by the anode (not shown). For convenience in making electrical connection to the anode, an axial lead 12 is often also provided. The grid structure is supported upon a tubular wall portion 13 which extends in close proximity to the anode support from the vacuum wall 1 3. This tubular wall is, in turn, sealed to annular flange 1'4. Annular flange 14 is attached to the relatively planar top of the generally cylindrical grid can which surrounds and closely approaches the anode on all sides. Under conditions of normal operation, conduction takes place between the cathode and anode through perforations in a planar disc-like portion on the opposite side of the cylindrical can-like structure to which flange 14 is attached. Intermediate the supported and perforated ends of the grid can are cylindrical side walls 15 which may be partially open or perforated to permit equalization of pressures inside and outside the grid can and which may be provided with a skirt 15a which extends below the opening of the cathode.

A cylindrical cathode 17 may be employed and usually consists of a tubular member having an oxide coating on the interior surface thereof and an open end partially closed by a disc-like baffle at that end nearer the grid structure. The-heater element may be coaxially located within the cathode structure for the purpose of activating the emitter. The opposite sides of the cathode and heater structure are connected to leads 18 and 19 which penetrate the vacuum envelope at stem press 20. Leads 18 and 19 are terminated externally of the vacuum envelope in flexible leads 21 and 22.

Also penetrating the stem press 26 are rod leads 23 and 24 which are terminated externally of the vacuum envelope in flexible leads 26 and 27. Leads 23 and 24 are connected to the gas generator by leads 28 and 29 respectively. Lead 28 is connected to one end of heater element 30 while lead 29 is connected to the metallic shell 31 or the shield 31a of the generator.

The generator is shown in greater detail in Figs. 2, 3 and 4. Referring to Fig. 2 it may be seen that heater 30 is contained in a ceramic dielectric cup 32 which is one form of the hollow cylindrical ceramic member already generally described. Advantageously, heater 30 is made of helical form and has an axial portion 30a which penetrates the bottom of the ceramic cup 32. The symmetrical and coaxial configuration of the generator is advantageously preserved by locating the cup 32 coaxially within the metallic shell 31. Between the cup and the shell the region is filled with sintered gas-generating material 33. Where the gas to be generated is hydrogen, the gas-generating material is advantageously the hydride of titanium, zirconium or hafnium. The present invention preferably employs large sintered particles of hydride which provide a porous mass through which gas can escape, even from the innermost parts of the mass 33 of the gas-generating material. Likewise the large sintered particles are more easily prevented from escaping from the gas generator. A large volume of gas-generating material may be employed in this form of structure. This arrangement also provides a relatively large surface area directly exposed to a heated surface per unit of volume of gas-generating material employed. To prevent the loss of the sintered material, porous annular pads or plugs 34 are inserted between the tubular shell 31 and the ceramic cup 32 at each end of the sintered mass. These pads are composed of some highly porous materials, such as metallic sponge or wool materials (e. g. steel wool). planar annuli 35 which may be welded to the shell 31 in order to hold the pads 34 and the sintered mass 33 in place. The annuli 35 are penetrated by holes or perforations 35a which permit the escape of gas from the generator.

As may be seen in Figs. 3 and 4, the open end of the ceramic cup is advantageously closed by a metallic disc 36 which is mechanically and electrically coupled and affixed to the shell 31 by means of tabs 36a which may be conveniently welded to the shell 31. A pair of angle brackets 37 may be afiixed to the disc 36 on opposite sides of the center hole through which the axial end 30b of the heater 30 is drawn. This end 30b is then advantageously welded or otherwise aflixed to angular brackets 37, thus electrically connecting the end 30b of the heater to the metallic shell 31. The generator is shielded from the tubes cathode by shield 31a (Figs. 1 and 3) which serves to minimize any heating of the gas generating material by the cathode.

In use, a potential applied across terminals 26 and 27 will cause a current to flow through lead 26, lead 24, lead 28 and through the heater 30, thence through the closure 36 to the shell 31 and through lead 29 to lead 23 and flexible lead 27. The heater Will cause the ceramic cup 32 to be heated to a temperature of 1100 to 1200 C. The heat thus produced is more uniform and is better distributed over a wider area than could be done with a heater coil directly in contact with the material or surrounding the gas-generating material rather than being surrounded by it. The heat produced will cause the breakdown of the generating material and the evolution of gas. For instance, where titanium hydride is employed, hydrogen gas will be evolved. The thorough heating of the material permits gas to be evolved throughout the body of the generating material and the sintered nature of the particles permits the escape of'the gas evolved from whatever region in which it may have origi- Holding these plugs in place are nated through the porous pads 34 and thence through the 5 perforations in the annuli 35.

Ionization effects may be observed within the vacuum 4 envelope to determine when more gas is needed within the envelope to support proper functioning of the tube. When additional gas is needed, the gas may be evolved in the manner described.

Various modifications within the scope of the claims are intended to be within the scope of the present invention. For instance, the gas generating material may be varied considerably. Although sintered material is preferred, powdered material or crystalline material or material in any other form may be employed. Rather than having the gases escape through the perforations in the metallic annuli, the gases may be forced to escape through a porous ceramic, e. g., the cup walls 32 where a permeable ceramic is employed. The plugs of metallic wool or similar porous material may be eliminated in certain instances, particularly where materials employed are not likely to be lost through the openings in the annuli. And, in general, the specific shape and configurations of the structure described may be widely varied within the scope of the claims.

I claim:

1. A gas generating device for use in electron tubes comprising a ceramic cup-like member, a tubular metallic enclosure for the cup-like member and in spaced relation therewith, a supply of gas generating material in the space between said enclosure and cup-like member, apertured annular retaining means between the enclosure and cup-like member at each end of the supply of gas generating material, a filament in the cup-like member and having one end extending through the base portion thereof, and a conductive member positioned at the open end of the cup-like member and connected to the adjacent end of the filament, said conductive member further being connected with the enclosure whereby a potential may be applied to the filament between the end thereof which penetrates the cup-like member and the enclosure.

2. A gas generating device for use in electron tubes comprising an axially disposed heater, :1 cylindrically shaped supply of gas generating material encircling the heater and having a relatively large surface area exposed to heat therefrom, a porous ceramic member separating the supply of gas generating material from the heater, and an enclosure for the device confining the supply and providing ready exit for gas generated by the supply when heated.

References Cited in the file of this patent UNITED STATES PATENTS 2,253,145 Smith Aug. 19, 1941 2,528,547 Reilly Nov. 7, 1950 2,709,247 Bell May 10, 1955 

